The present invention relates to a safety device for vertically moving load carrier, including a safety detent and a safety rack. In case the transmission belt is accidentally broken, the safety detent is forced to engage with the safety rack so as to prevent the load carrier from abruptly dropping down to cause accident.
FIGS. 1 and 2 show a conventional vertically moving load carrier often used in a general packing machine, elevator, crane, parking apparatus, etc. Such load carrier basically includes a pair of vertical columns 1 and a retainer 2.
The vertical column 1 has a predetermined height and is disposed with a driving shaft 11 and a driven shaft 12 respectively at top section and bottom section. The driving shaft 11 is driven by a driving means 13. An circular flexible circulating transmission belt 14 (such as a chain, a leather belt or a steel cord) is sealedly disposed between the driving shaft 11 and the driven shaft 12. The driving means 13 can be an electric motor.
The retainer 2 is secured at a predetermined position of the transmission belt 14 and is only vertically slidable along the vertical column 1. The retainer 2 has a load platform 21 for receiving a load 22 (such as an article, person or car). When the driving means 13 drives the driving shaft 11, via the transmission belt 14, the retainer 2 is lifted from a lower first position H1 to a higher second position H2 or is lowered from the second position H2 to the first position H1.
The conventional device has a most serious problem, that is, unsafety. Especially, when the retainer 2 is lifted or lowered, in case the load 22 is too heavy and the transmission belt 14 is accidentally broken apart, the load will abruptly drop down to cause injury or death of persons or damage of articles.
A safety device (not shown) used in the conventional car parking apparatus includes similar vertical column structure. The safety device further includes an upper sprocket, a lower sprocket, a chain and a parking platform. In addition, a vertical dropproof rack is disposed on one side of the vertical column. The parking platform is equipped with a safety detent and an electromagnetic valve near the dropproof rack. Such safety device is operated in such a manner that when the platform goes up, the electromagnetic valve is not energized and the safety detent is moved upward along with the platform one tooth by one tooth in contact with the dropproof rack. When going down, the electromagnetic valve is energized to pull back the safety detent from contacting with the dropproof rack, permitting the parking platform to move downward.
However, the above structure still has two major shortcomings as follows: 1. The parking platform is prevented from accidentally dropping only in rising state. While when moving downward, the safety detent does not contact with the dropproof rack. That is, it has no any security. This is extremely dangerous. 2. When rising, the safety detent keeps in contact with the dropproof rack and is quite subject to abrasion.